Timber Roof Blueprints Felting A Timber Shed Roof?

Felting a timber shed roof? - timber roof blueprints

Building a wood shed!
12x10 in my garden.
Two questions?
1 - I have put a concrete slab on the ground or above the wet concrete road blocks .. If left to Ireland and we have a lot of rain ..

2 - I do not think I know to do the roof nails on his knees, but nothing at the seams?
Everyone felt a shed that we have a consultation?